[world-vercel] Use undici dispatcher for VQS client

.changeset/weak-cats-admire.md

@@ -0,0 +1,5 @@
+---
+"@workflow/world-vercel": patch
+---
+
+Use undici dispatcher for queue client

packages/world-vercel/src/http-client.ts

@@ -8,19 +8,19 @@ let _dispatcher: RetryAgent | undefined;
  * - Connection pooling (up to 8 connections per origin)
  * - Retry: Automatic retry on 429/5xx or network errors with exponential backoff
  *   - Observes Retry-After header if received and lower than 30s
- *
- * Note: HTTP/2 is disabled because undici's experimental H2 support hangs
- * in certain Vercel runtime environments (sveltekit). HTTP/1.1 pipelining
- * is also disabled (pipelining: 1) because it causes head-of-line blocking
- * that deadlocks the webhook respondWith mechanism. The primary benefits
- * from undici here are retry logic and connection pooling.
  */
 export function getDispatcher(): RetryAgent {
   if (!_dispatcher) {
     _dispatcher = new RetryAgent(
       new Agent({
         connections: 8,
         keepAliveTimeout: 10_000,
+        // H2 is specifically incompatible with SvelteKit on Vercel prod. Everything else
+        // runs fine.
+        // TODO: Investigate/fix the failure on SvelteKit so we can re-enable H2.
+        allowH2: false,
+        // HTTP/1.1 pipelining is disabled (pipelining: 1) because it causes
+        // head-of-line blocking that deadlocks the webhook respondWith mechanism.
         pipelining: 1,
       }),
       {

packages/world-vercel/src/queue.ts

@@ -8,6 +8,7 @@ import {
   ValidQueueName,
 } from '@workflow/world';
 import * as z from 'zod';
+import { getDispatcher } from './http-client.js';
 import { type APIConfig, getHeaders, getHttpUrl } from './utils.js';
 
 const MessageWrapper = z.object({
@@ -84,6 +85,7 @@ export function createQueue(config?: APIConfig): Queue {
 
   const clientOptions = {
     region,
+    dispatcher: getDispatcher(),
     ...(usingProxy && {
       // final path will be /queues-proxy/api/v3/topic/...
       // and the proxy will strip the /queues-proxy prefix before forwarding to VQS

pnpm-workspace.yaml

@@ -11,7 +11,7 @@ catalog:
   "@types/node": 22.19.0
   "@vercel/functions": ^3.4.3
   "@vercel/oidc": 3.2.0
-  "@vercel/queue": 0.1.1
+  "@vercel/queue": 0.1.4
   "@vitest/coverage-v8": ^4.0.18
   ai: 5.0.104
   esbuild: ^0.27.3